Spinnerette pack for melt spinning



Jan. 24, 1967 E. A. MARTIN 3,

' SPINNERETTE PACK FOR MELT SPINNING I Filed April 2, 1965 INVENTOR. E.A. MARTIN BYMfW ATTORNEY United States Patent 3,299,472 SPINNERE'ITE PACK FOR MELT SPINNING Eugie A. Martin, Gulf Breeze, Fla., assiguor to Monsanto Company, St. Louis, Mo., a corporation of Delaware Filed Apr. 2, 1965, Ser. No. 444,986 4 Claims. (Cl. 18-8) This invention relates to spinnerette packs. More partioular-ly, it pertains to a spinnerette pack for melt spinning having a substantially dome-shaped pack cavity therein.

Most customary spinnerette packs have pack cavities of such shape that there are areas within which prevent tree polymer flow, thus resulting in stagnant polymer flow in certain areas within such cavity. Stagnant polymer remains in a pack cavity for extended periods, much longer than free flowing polymer. Because of being held up, stagnant polymer polymerizes to a higher degree than free flowing polymer. This stagnant, highly polymerized polymer in time breaks loose and attempts to pass out of the pack through the capillaries in the spinnerette plate. Thus, the capillaries become plugged, resulting in uneven polymer ilow and a reduced number of filaments in the filament bundle produced by the spinnerette pack.

Furthermore, in the greater portion of contemporary spinnerette packs, pressure distribution on the upstream side of the spinnerette plate is quite uneven. This condition is thoroughly undesirable, for the optimum condition for melt spinning through a spinnerette plate is equal pressure at the entrance to and equal ilow through every capillary in the spinnerette plate. Equal pressure and equal flow through identical capillaries within a spinnerette plate produce filaments of substantially equivalent size and quality, thus a better quality filament bundle results.

Therefore, it is an object of this invention to provide a spinnerette pack having a cavity of such shape that stag nant polymer areas are substantially eliminated.

A further object is the provision of a spinnerette pack having a pack cavity wherein the pressure at the entrance to every capillary in the spinnerette plate is substantially equal.

Other objects will become apparent from the following descriptive material.

In the drawing, FIGURE 1 is an elevational view, in section, of the inventive spinnerette pack mounted in a pack holder. FIGURE 2 is a top plan view of the spinnerette plate shown in FIGURE 1. The dotted circles represent radial distances rather than structure.

In general and in accordance with FIGURE 1, the above objects are achieved in the provision of spinnerette pack mounted within pack holder 12 and containing substantially dome-shaped pack cavity 14. Pack cavity 14 contains inert packing material 16, has a base 18, and includes a polymer entrance port 20 substantially at the top thereof. A screen 22 is fitted across pack cavity base 18. spinnerette plate 24 containing capillaries 26 is sealingly clamped into position below pack cavity base 18 and screen 22.

With particular detailed reference to FIGURE 1, spinnerette pack 10 is fixedly positioned within pack holder 12. Substantially dome-shaped pack cavity 14 is connected through polymer entrance port 20 and conduit 28 to a suitable source of molten polymer under high pressure. Gasket 30 makes a seal between pack holder 12 and spinnerette pack 10. spinnerette plate 24, containing a plurality of capillaries 26, is held in position below pack cavity base 18. A screen 22, generally a wire screen, is positioned across base 18 to prevent particles of finely divided inert material 16 from entering capillaries 26. This finely divided inert material can be made of metal, ceramic, glass, and the like materials. *I-Iowever, sand is generally preferred. In conjunction with the finely divided particles, it is preferred that the entrances to capillaries '26 should be counterbored to a diameter that is larger (6-5 times as large) compared to the average diameter of the packing material.

Pack holder 10, finely divided inert material 16, screen 22, and spinnerette plate 24 are fixed in position by clamp 32 held by bolts 34 bolted into pack holder 12. Gasket 36 seals the joint between spinnerette pack 10 and spinnerette plate 24.

The centers of both polymer entrance port 20 and spinnerette plate 24 are axially aligned on centerline 38. The distance from centerline 38 to the wall of pack cavity 14 at base 18 is shown as base radius R. Intermediate base radius r is representative of any radial distance from centerline 38 at pack cavity base 18, wherein the value of r is greater than zero but less than base radius R.

The distance 'from pack cavity base 18 to polymer entrance port 20 is shown as height h which is assigned the value of unity and is to be taken as the reference dimension.

The general shape of the pack cavity of the spinnerette pack is dome-like. Nevertheless, the preferred domeshaped cavities take the form of Rankin Bodies (reference: Streeter, Fluid Dyna-mics, McGraw-Hill Book Co., New York, 1948, p. 59). The preferred pack cavity shape is given by a curve rotated about centerline 38, which is also an axis of symmetry. This curve is defined by the equation a: 1 (x 1) lam 4W Equation 1 wherein x is a height above pack cavity base 18 on centerline 38 within pack cavity 14 and has a value from zero to unity; y is the radial distance from the upper limit of height x to the Walls of pack cavity 14; C is a positive number greater than zero but less than twice C C is a finite positive number. C and C must satisfy Equation 2 (set forth below) for any given base radius R.

When x equals zero, y equals base radius R and Equation 1 reduces to ing to the equation R on Equation 3 wherein N is the number of capillaries within an intermediate base radius r (defined above), N is the total number of capillaries within base radius R, Qg is the total polymer flow through the pack cavity, and Q is the polymer flow through the area circumscribed by the above noted inter-mediate base radius r. The value of Q /Q can be determined by the equation Equation 4 Patented Jan. 24, 1967 wherein Q Q r, R, and C are as defined hereinbefore. For any particular spinnerette pack the values for C and C must be the same for every equation set forth herein.

Generally, the total number of capillaries within base radius R is determined by the number of filaments that are to be produced. From this information and from Equation 4 the number of capillaries N within an intermediate base radius r can be calculated. If the number is calculated to be a whole number plus a tfraction, the fraction should be rounded off to the nearest whole number.

An example of the invention is set forth hereinafter. This example is intended to illustrate and should not be construed as a limitation upon the invention.

EXAMPLE In this exemplary spinnerette pack cavity, height h is taken as unity and is the reference dimension. Base radius R is 0.655 of the pack cavity height. There are 101 capillaries through the spinnerette plate and constant C is 0.800 and constant C is 0.735, both constants being dimensionless. Table 1 :is a tabulation of various values of x (height above the pack cavity base) with the corresponding values of y (radial distance from the upper limit of height at to the walls of the pack cavity). The values of x were arbitrarily set and the corresponding radial distances y were calculated by using Equation 1. At x equals zero, y equals the above base radius, 0.655.

Table 1.Valucs of y for certain values of x x y x y 0.000 0.655 0.600 0.560 0.100 0.653 0.700 0.519 0.200 0.649 0.800 0.456 0.300 0. 636 0.900 0.351 0.400 0.619 0.95 0.259 0.500 0.596 1.000 0.000

To locate the capillaries in the spinnerette plate, that portion of the surface of the plate filling over the pack cavity base corresponding to the radius of the pack cavity base, 0.655, was measured to determine a series of concentric circles having radii of 0.1, 0.2, 0.3, 0.4, 0.5, and 0.655 of the reference dimensions. Then by Equation 4 the flow through each circle was calculated. The capillaries were then spaced so that the number between any two successive circles has the same ratio to the total number of capillaries as the flow between the circles does to the total flow. Fractional values were rounded to the nearest whole number. The capillaries which were calculated to be between any two successive circles were then equally spaced in the center of and around the annular ring formed between the successive circles. Table 2 shows the number of capillaries within the various selected radii. The number of capillaries shown is the total number of capillaries within the circle bounded by each radius.

Table 2.Capillaries within circles of given radii Capillaries Equal pressure, resulting in equal flow, produces filaments of equal size, a quite desirable result.

Furthermore, the pack cavity of the instant spinnerette pack has no areas therein Where polymer will stagnate, thereby producing a highly polymerized material called gel which tends to plug capillaries when it breaks loose and attempts to pass through the capillaries. A still lurther advantage is that in the instant spinnerette pack there is no necessity for a distribution plate; therefore the apparatus is simpler than most spinnerette packs in present use.

The invention has been described by referring to specific illustrations and embodiments. Nevertheless, no limitation should be placed upon the scope of the invention other than that of the appended claims.

What is claimed is:

' 1. A spinnerette pack for melt spinning filaments from molten polymer comprising in combination in fixed adjacent relationship:

(a) walls defining a substantially dome-shaped spinner ette pack cavity having finely divided inert material therein, a polymer entrance port substantially at the top thereof, and a base of radius R, the center of both said port and said base being axially aligned on a centerline;

(b) screening means across said base of said domeshaped cavity; and

(c) a spinnerette plate in sealed relationship with said walls defining said base of said cavity, said spinnerette plate having a plurality of capillaries therethrough, the number of capillaries within an intermediate base radius r being determined by the equation wherein N is the total number of capillaries through said spinnerette plate within said base radius R, N is the number of capillaries within intermediate base radius r wherein r is less than base radius R but more than zero, Q is the total polymer flow through said cavity and Q is the polymer flow through the area of the base circumscribed by intermediate base radius r.

2. A spinnerette pack for melt spinning filaments from molten polymer comprising in combination in fixed adjacent relationship:

(a) walls defining a substantially dome-shaped spinnerette pack cavity having a height of unity, a substantially circular base of radius R, and a polymer entrance port substantially at the top thereof, said cavity having finely divided inert material therein, the center of both said entrance port and circular base being axially aligned on a 'centerline, said walls being defined by a curve rotated about said centerline, said curve being defined by the equation wherein x is a height above said base on said centerline within said cavity having a value from zero to unity,

y is the radial distance from the upper limit of said height above said base to said walls,

C is a positive number from zero to less than twice C C is a finite positive number, wherein said C and C must satisfy the equation for any given value of base radius R; (b) screening means across said base of said cavity; (c) a spinnerette plate in sealed relationship with said walls defining said base of said dome-shaped cavity, said spinnerette plate having a plurality of capillaries therethrough, the number of capillaries within an intermediate base radius r being determined by the equation Q! NY NR QR wherein N is the total number of said capillaries in said spinnerette plate Within said base radius R,

N is the number of capillaries in said spinnerette plate within intermediate base radius 2' when r is less than R but more than zero,

Q is total polymer flow through said cavity and Q is the polymer flow through the area of the base circumscribed by said intermediate base radius r.

References Cited by the Examiner UNITED STATES PATENTS 2,078,509 4/1937 Prutton 188 2,229,489 1/1941 Barnard 18--8 3,090,490 5/1963 Yocum 210-446 X 3,104,419 9/ 1963 La Forge 188 WILLIAM J. STEPHENSON, Primary Examiner. 

1. A SPINNERETTE PACK FOR MELT SPINNING FILAMENTS FROM MOLTEN POLYMER COMPRISING IN COMBINATION IN FIXED ADJACENT RELATIONSHIPS: (A) WALLS DEFINING A SUBSTANTIALLY DOME-SHAPED SPINNERETTE PACK CAVITY HAVING FINELY DIVIDED INERT MATERIAL THEREIN, A POLYMER ENTRANCE PORT SUBSTANTIALLY AT THE TOP THEREOF, AND A BASE OF RADIUS R, THE CENTER OF BOTH SAID PORT AND SAID BASE BEING AXIALLY ALIGNED ON A CENTERLINE; (B) SCREENING MEANS ACROSS SAID BASE OF SAID DOMESHAPED CAVITY; AND (C) A SPINNERETTE PLATE IN SEALED RELATIONSHIP WITH SAID WALLS DEFINING SAID BASE OF SAID CAVITY, SAID SPINNERETTE PLATE HAVING A PLURALITY OF CAPILLARIES THERETHROUGH, THE NUMBER OF CAPILLARIES WITHIN AN INTERMEDIATE BASE RADIUS R BEING DETERMINED BY THE EQUATION 